Pulverulent corn-steep

ABSTRACT

The invention relates to a pulverulent corn-steep without a drying substrate, said corn-steep containing lactic acid. It also relates to a method of obtaining this pulverulent corn-steep as well as to its use in the fermentation industry.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Divisional patent application of U.S.patent application Ser. No. 09/542,119 filed Apr. 4, 2000, thedisclosure of which is being incorporated herein by reference in itsentirety.

FIELD OF THE INVENTION

[0002] The present invention relates to a pulverulent corn-steep withouta drying substrate.

[0003] It also relates to a particular method of preparing saidpulverulent corn-steep and to its uses in industry.

BACKGROUND OF THE INVENTION

[0004] Corn-steep, a term frequently used by the person skilled in theart, refers to the concentrated steep waters which result from thesteeping of maize.

[0005] The steeping of maize in water is the first step in theextraction of starch in wet starch works. This steeping allows theswelling of the maize grains and the elimination of highly fermentablesoluble matter contained in these grains. It consists in keeping themaize in silos for a given period of time within hot water containing asmall quantity of sulphurous anhydride, this in order to facilitate thelater separation of protein, cellulose and starch and, moreover, to stopthe growth of undesirable micro-organisms.

[0006] Two essential phenomena take place simultaneously duringsteeping: the first consists in a diffusion of soluble matter from themaize grain towards the steep water whilst the second consists in afermentation of this soluble matter in the steep water by lacticbacteria, the steeping conditions (presence of sulphites, reducingsugars, temperature) being favorable for the speedy development of thisbacterial flora.

[0007] The main interest of these concentrated steep waters, usuallycalled corn-steep by the skilled person, is their composition inessential nutrients, resulting from the transfer of the soluble matterof the grain. These nutrients constitute factors which favor the growthof micro-organisms as well as the production of secondary metabolitesand make the corn-steep an ideal source of nutrient substances in thefermentation industries.

[0008] Indeed, corn-steep constitutes a source of choice of organicnitrogen through the distribution and the forms of its amino acids:free, peptide, protein, as well as a source of carbon (lactic acid) andphosphate (phytic acid) with a delayed effect. A significant content ofvitamin and trace elements completes the interest of corn-steep as anutrient source for the growth of micro-organisms and the induction ofsecondary metabolites when the corn-steep is associated with one orseveral sources of carbon (glucose, maltodextrin, starch, sucrose . . .).

[0009] Moreover, it constitutes a nutrient source which is relativelycheap by comparison with yeast extracts which represent the referencematerial in this field and which are also used in human and animalfeeding.

[0010] Furthermore, it is known that the use of corn-steep to replacecomplex nitrogen sources such as cotton or soya proteins, makes itpossible to increase substantially antibiotic production yields.

[0011] However, corn-steep in liquid form presents problems of settlingin the course of time, which is especially bothersome for transporting,storing and pumping the product. It must be stored in stirred andthermostatically controlled tanks to limit the development of itscomposition. This is all the more true when corn-steep is consumed insmall quantities at a time by certain fermentation industries. In thiscase, it is particularly important to control its preservation.Obtaining corn-steep in dry form has then been considered.

[0012] Corn-steep has a water content of 45 to 55%. Evaporation toeliminate more than half of the water which it contains cannot beconsidered in view of the cost of evaporation on the one hand and thesensitivity to heat of certain nutrients on the other hand.

[0013] Drying through atomisation of liquid corn-steep has then beenstudied.

[0014] This technique, very widespread in the industry, has allowed thedrying of products well known as difficult to dry, such as productswhich are sensitive to heat or highly hygroscopic. However, in the caseof corn-steep, the person skilled in the art has met with gluingproblems. Indeed, if the drying of certain products does not present anyproblems, i.e. the powder comes steadily out of the drying chamber ortower and has satisfactory appearance and flow properties, the liquidcorn-steep, on the other hand, being rich in amino acids and hygroscopicsubstances, is subject to gluing.

[0015] This gluing manifests itself in deposits at various levels of thedrying chamber and its ancillary equipment, deposits which generatelosses and a deterioration of the product which can require stoppingproduction with cleaning cycles which are costly in time, material andlabour. Gluing can also happen downstream of drying when the powder,after a more or less lengthy storing period, loses its fluidity andforms lumps.

[0016] It is therefore very difficult to atomise corn-steep because ofthe particularly hygroscopic nature of the organic acids and the saltswhich it contains and especially the potassium lactate which is presentin a large proportion (Corn Chemistry and Technology—K. N. WRIGHT466-467).

[0017] To overcome these gluing problems, methods, sometimes empiricalones, have been applied at the industrial level, such as the addition tothe product to be atomised of drying substrates, anti-agglomeratingagents or dessicating powders.

[0018] In the food-processing industries, substrates frequently used aremaltodextrins and glucose syrups. However, their incorporation rates arelimited by the diluting effect which they exert on the product and bytheir high cost. Furthermore, such products cannot be subjected to alater heat treatment, such as sterilisation, as their high content offree sugars makes them subject to caramelization. Moreover, thesecompositions are highly hygroscopic which leads to lumping phenomenaduring storage.

[0019] It was then proposed in patent U.S. Pat. No. 2,859,114 that maizefibres be mixed with corn-steep so that it is absorbed by these fibres,thus making a drying operation possible. However, this method has thedisadvantage of bringing to the corn-steep a high content of insolublematter which is not desirable in the applications envisaged, especiallyfermentation.

[0020] Indeed, such a product very quickly shows settling phenomenaduring storage and through this a heterogeneous distribution of nutrientsubstances.

[0021] Furthermore, the product shows at the end an insufficientcorn-steep concentration.

[0022] Other solutions, like the one described in the patent U.S. Pat.No. 3,655,396 consist in completely eliminating the lactic acid from thecorn-steep. The lactic acid having indeed been blamed for the problemsof drying corn-steep without it being clearly explained, it iseliminated with yeasts able to metabolise it, the culture mediumobtained being afterwards dried on drums or through atomisation.

[0023] However, such a method has the drawback of depriving corn-steepof an important source of carbon on the one hand, but also of aprecursor which is particularly interesting in the culture of diauxicmicro-organisms.

[0024] There was therefore the need for a dry form of corn-steep withretained nutrient value and solubility.

SUMMARY OF THE INVENTION

[0025] Strengthened by this assessment, the inventors have thereforesought to perfect a pulverulent corn-steep, the qualities of which areretained and without the defects previously described for corn-steeps inpowder form according to prior art.

[0026] And it is to the credit of the inventors that they have succeededagainst all expectations, after carrying out in-depth research on thesubject, in preparing a pulverulent corn-steep without being faced withgluing problems, this pulverulent corn-steep being without the defectsnoticed for the corn-steeps in powder form according to prior art,whilst retaining its initial qualities. The inventors have highlighted,in a surprising and unexpected manner, that such pulverulent corn-steepcan be prepared without a drying substrate and without previousseparation treatment, in special conditions starting from liquidcorn-steep, with an atomisation process which had never made it possiblein the past to obtain directly and without gluing corn-steep in powderform with the nutrient qualities intact, improved even, withsatisfactory solubility and without any tendency to become lumpy.

[0027] It is all the more surprising that the atomisation of liquidcorn-steep appeared, according to the patents U.S. Pat. Nos. 2,859,114and 3,655,396, impossible without a drying substrate or withouteliminating a fraction of the corn-steep.

MORE DETAILED DESCRIPTION

[0028] The invention relates, therefore, in the first place to apulverulent corn-steep without a drying substrate. The term “dryingsubstrate” designates the soluble or insoluble organic compounds likelyto absorb liquid corn-steep or to modify its activity in water. Thesesubstrates known to the skilled person are in particular plant fibres,spent grain, brans, proteins, polysaccharides, carbohydrates,dessicants.

[0029] The essential feature of the pulverulent corn-steep according tothe invention stems from the fact that it contains lactic acid. Lacticacid is understood as the D and L forms of lactic acid as well as itssalts. Preferably, this lactic acid content is greater than or equal to5% by weight dry or, even more preferably, equal to or greater than 10%by weight dry. Consequently it retains its qualities in relation to thepulverulent corn-steeps according to prior art from which the lacticacid would have been eliminated and does not have the drawbacks ofinsolubility or caramelization of the corn-steeps according to prior artdried on substrates of cellulose fibres or maltodextrins.

[0030] Advantageously, pulverulent corn-steep according to the inventionhas a metal ions content of between 1 and 5% by weight (dry/dry).Preferably this content is between 2 and 4% by weight (dry/dry).

[0031] The inventors have indeed demonstrated after long research thatthis second characteristic advantageously made it possible to obtain apulverulent corn-steep which retained its initial properties andnutrient qualities.

[0032] Thus, beyond a 5% content in metal ions, corn steep becomesunusable in a fermentation medium as it brings an excess of metalsunfavorable to the growth of micro-organisms.

[0033] Moreover, below a 1% content in metal ions, it is not possible toobtain a pulverulent corn-steep without the help of a drying substrateor without eliminating some of its constituent elements, such as lacticacid.

[0034] It is preferred that the metal ions are chosen from the groupconstituted of zinc, magnesium, calcium, strontium, barium or lithiumsalts, on their own or mixed with one another. In particular, magnesiumsalts are perfectly suitable. Indeed, these constitute an input in Mg²⁺ions, the fundamental role of which in the growth and metabolism ofnumerous micro-organisms is known. This cation is indeed vital in thestabilisation of the cellular structure and involved in most of themetabolic mechanisms as an enzymatic cofactor.

[0035] Because of this, the nutrient qualities of pulverulent corn-steepaccording to the invention are not only preserved but also improved. Itis understood then that these nutrient qualities combined with the easeof storing and implementation are an unquestionable advantage, forinstance, in the preparation of culture media intended for fermentation.

[0036] The pulverulent corn-steep according to the invention has alsoother advantageous characteristics. One can mention its very goodaptitude for being compressed and its very good aptitude for being mixedwith other products.

[0037] The invention relates in the second place to a method ofpreparing a pulverulent corn-steep without a drying substrate andcontaining lactic acid.

[0038] The pulverulent corn-steep according to the invention is likelyto be obtained by carrying out an enrichment of a liquid corn-steep withat least one metal salt before atomisation.

[0039] It has been noted, against all expectation, that such anenrichment step allowed the atomisation of the liquid corn-steep withoutgenerating gluing or lumpiness problems and without eliminatingpreviously the lactic acid which it contains.

[0040] Indeed the inventors have demonstrated that the drying problemsmet in the methods of prior art were due to the fact that the potassiumlactate present in great quantities in the corn-steep could not becrystallised. In enriching the corn steep with metal salt, the potassiumlactate is displaced, through the salt effect, towards a form of lactatewhich can be crystallised. The corn-steep thus enriched is thereforeeasy to atomise, without it being necessary to add a drying substrate orto eliminate the lactic acid or other compound constituting thecorn-steep.

[0041] The pulverulent corn-steep according to the invention is capableof being obtained according to a multitude of variants of the method butespecially through a method comprising the following steps:

[0042] enrichment of the liquid corn-steep with at least one metal salt,

[0043] atomisation of the enriched liquid corn steep,

[0044] recovery of the pulverulent corn-steep thus obtained.

[0045] Concerning the enrichment of the liquid corn-steep, it ispreferred that the metal salt is chosen from the group consisting ofzinc, magnesium, calcium, strontium, barium and lithium salts. Accordingto a preferred embodiment of the invention, magnesium oxide is chosen.As an indication, there is added to the liquid corn-steep a quantity ofMgO of approximately 3% in dry weight expressed relative to the drymatter of the liquid corn-steep (dry/dry).

[0046] The liquid corn-steep used in the method according to theinvention can, in particular, be the one described in patent U.S. Pat.No. 4,359,528 or again those described in patent applications EP 724 841and EP 819 702 of which the Assignee is the owner.

[0047] As regards atomisation of the corn-steep enriched with metalsalt, any type of material known to the skilled person can be used.

[0048] The inventors have demonstrated that pulverulent corn-steepaccording to the invention could be manufactured advantageously using,for instance, an atomisation tower of the NIRO type.

[0049] Advantageously, one can choose an air intake materials such thatthe temperature of the air leaving the tower will be between 80 and 150°C.

[0050] The pulverulent corn-steep obtained according to the method ofthe invention can be afterwards made into tablets, for instance, inalternating presses in the presence of a lubricant.

[0051] The pulverulent corn-steep according to the invention can be usedwith advantage as a nutrient substance in the preparation of culturemedia for the fermentation industry. It can also be used in the fieldsof food industry or alimentation, animal nutrition or other fields.

[0052] Unlike the pulverulent corn-steeps of prior art, the corn-steepaccording to the invention retains its initial biochemicalcharacteristics. Furthermore, it possesses the advantageouscharacteristic of being compressible which is of particular interest inindustrial practice because of the risks and disadvantages linked tohandling powders. Moreover, the tablet form permits meticulous dosage inthe preparation of culture media.

[0053] The invention will be understood even better with the aid of thefollowing examples which are not restrictive and which account for onlycertain embodiments and for certain advantageous properties of thepulverulent corn-steep according to the invention.

EXAMPLE I Preparation of Pulverulent Corn-Steep According to theInvention.

[0054] A liquid corn-steep is prepared with 50% dry matter, implementingthe method described in patent EP-A-0 819 702 in the name of theAssignee. To this is added 3.2% by weight (dry/dry) of MgO in the formof a 100 g/l suspension in a tank with a thermostat at 50° C., whilststirred.

[0055] The pH of the liquid corn-steep enriched with MgO is 5.7.

[0056] Then, atomisation is carried out in a NIRO tower under thefollowing conditions:

[0057] input temperature: 200° C.

[0058] output temperature: 96° C.

[0059] speed of turbine: 15,000 rotations per minute

[0060] evaporation capacity: 80 litres per hour

[0061] The lactic acid content of the corn-steep obtained is 14% byweight.

[0062] The particles do not stick to the walls of the atomising chamber.

[0063] The powder is dense and falls down quickly from the cyclone.

EXAMPLE 2 Application of the Pulverulent Corn-Steep According to theInvention to the Growth of Organisms

[0064] The study described below consists in following the increase inthe number of cells according to time in a culture medium containing agiven concentration of the pulverulent corn-steep according to theinvention. This is done in comparison with culture media containing thesame equivalence in nitrogen brought by other sources.

[0065] The study relates to the growth of a strain of Saccharomycescerevisiae. The analysis of the culture worts is carried out at 0, 24and 48 hours of incubation by determining cellular mortality by fluxcytometry (CHEMFLOW CHEMUNEX).

[0066] A preculture medium is prepared by adding to demineralised water50 g/l glucose, 5 g/l liquid corn-steep with 50% dry matter, 5 g/lpeptone. 3 g/l KHPO₄ and 1 g/l MgSO₄, 7H₂O. The medium is sterilised for20 minutes at 120° C. after adjustment of the pH to 5.7. 50 ml of mediumare then seeded by a loop of cells coming from a nutrient medium treatedwith gelose CGA (MERCK).

[0067] The preculture is incubated for 24 hours at 30° C. whilst beingstirred at 250 rotations per minute.

[0068] A culture medium is prepared by adding to demineralised water 100g/l glucose and 5 g/l pulverulent corn-steep according to the invention.

[0069] By way of comparison, culture media are prepared with 10 g/lliquid corn-steep with 50% dry matter, 10 g/l hydrolysed not atomisedliquid corn-steep (with 50% dry matter) as described in patent EP-A-819702 in the name of the Assignee, or 3 g/l yeast extract (YEAST EXTRACTmarketed by the company DIFCO). The volume of the medium is 50 ml inErlenmeyer flasks of 500 ml with 4 baffles at the bottom. These mediaare sterilised for 20 minutes at 120° C.

[0070] Each of these media is seeded with 5 ml of the same preculture ofS. cerevisae. The incubation is carried out at 30° C. whilst stirring at250 rpm for 48 hours.

[0071] The analysis by flux cytometry is made according to the protocollaid down by the company CHEMUNEX for the use with of the apparatus ChemFlow Auto System 3.

[0072] Results

[0073] The results are expressed as a percentage of dead cells presentin the total population (estimated at 10⁸ cfu/g). 0 h 24 h 48 h LCS (*)41.8% 11.4% 12.9% Hydrolysed not atomised LCS 41.8% 10.5% 11.4% CS ofthe invention 41.8% 11.2% 11.8% Yeast extract 41.8% 46.2% 56.4%

[0074] The results show better preservation of cellular viability forcells cultivated on atomised pulverulent corn-steep according to theinvention compared with cells cultivated on yeast extract.

[0075] These same results show, for cells cultivated on corn-steepaccording to the invention, preservation of cellular viability similarto that obtained for cells cultivated on liquid corn-steep, hydrolysedor not.

[0076] Atomising has therefore not altered in any way the nutrientqualities of the corn-steep. Moreover, the significant density of thepowder permits easier handling than the yeast extract, in particularwhen weighing.

25. A pulverulent corn-steep containing no drying substrate, saidcorn-steep containing lactic acid and having a lactic acid contentgreater than or equal to 10% by weight of dry matter.
 26. Thepulverulent corn-steep according to claim 25, having a metal ionscontent of between 1 and 10% by weight (dry/dry).
 27. The pulverulentcorn-steep according to claim 26, wherein the metal ions content isbetween 2 and 5% by weight (dry/dry).
 28. The pulverulent corn-steepaccording to claim 25, wherein the metal ions are selected from thegroup consisting of zinc, magnesium, calcium, strontium, barium, lithiumsalts, on their own or mixed with one another.
 29. The pulverulentcorn-steep according to claim 28, wherein the metal ions are magnesiumsalts.
 33. A tablet comprising a pulverulent corn-steep according toclaim
 25. 34. The pulverulent corn-steep according to claim 25, whereinsaid corn-steep is used as a nutrient substance in the fermentationindustry.
 35. The tablet according to claim 33, wherein said tablet isused as a nutrient substance in the fermentation industry.